Chapter 7: The Axial Skeleton

1. Chapter 7: The Axial Skeleton

2. Divisions of the Skeleton Axial---bones that lie around the longitudinal axis of body. Appendicular�bones of the upper and lower limbs plus bones forming the girdles.

3. Types of Bones Long bones Have greater length than width Has a shaft and variable number of extremities Has mostly compact bone in the diaphysis and spongy bone in the epiphysis.

4. Types of Bones Short bones Are equal in length and width (cube shape) Is mostly spongy bone except at the surface which has compact bone. Examples: Carpal bones of the wrist and tarsal bones of the ankle.

5. Types of Bones Flat bones Are thin and composed of two parallel plates of compact bone enclosing a layer of spongy bone. Provide protection and areas for muscle attachment. Examples: Skull bones, sternum, ribs and scapulae

6. Types of Bones Irregular bones Vary in size and shape. Vary in the amount of compact and spongy bone. Examples: Vertebrae, hip bones, facial bones, and calcaneus (heel bone).

7. Types of Bones Sesamoid bones Develop in certain tendons to protect against friction, tensions and stress. They are small in diameter (a few mm). Change the direction of pull of a tendon. Examples: patella

8. Types of Bones Sutural bones Small bones located in sutures between cranial bones. Number varies from person to person.

9. Bone Surface Markings Depressions and openings�used to form joints or allow the passage of soft tissues such as blood vessels and nerves. Fissure�Narrow slit through which blood vessels and nerves can pass. Fossa�shallow depression Foramen�Opening through which blood vessels and nerves can pass. Sulcus�furrow that accommodates a blood vessel, nerve or tendon. Meatus�tubelike opening.

10. Fissures and foramens

11. Meatus

12. Sulcus and fossa

13. Bone Surface Markings Processes�projections or outgrowths that form joints Condyle�large round protuberances Facet�smooth flat articular surface Head�rounded articular projection supported on the neck

14. Bone Surface Markings Processes�or serve as attachment points for connective tissue. Spinous process Crest Tuberosity

15. Bone Surface Markings Processes�or serve as attachment points for connective tissue. Epicondyle Line Trochanter

16. Bone Surface Markings Processes�or serve as attachment points for connective tissue. Tubercle

17. Skull bones Cranial bones�enclose and protect the brain Facial bones�nasal (2), maxillae (2), zygomatic (2), mandible, lacrimal (2), palatine (2), inferior nasal conchae (2), and vomer.

18. Skull cavities Cranial cavity Nasal cavity Orbits

19. Cranial bones Frontal bones forms the forehead and the roof of the orbit. Parietal bones form the sides. Temporal bones form the inferior lateral part of the cranium The mandibular fossa and articular tubercle articulate with the mandible to form the temperomandibular joint. Houses the internal bones of the ear

20. Cranial bones

21. Cranial bones Occipital bone forms the posterior part and most of the base of the skull.

22. Cranial bones Sphenoid bone is the keystone the skull base, articulating with all the other cranial bones.

23. Cranial bones Ethmoid bone is a spongelike bone that forms: Part of the anterior portion of cranial floor Medial walls of the orbits Superior portion of the nasal septum Most of the superior walls of the nasal cavities.

24. Ethmoid bone

25. Facial bones Maxillae form the upper jaw bone. Articulate with every bone of the face but the mandible. Forms the bony roof of the mouth Palatine bone form the posterior part of the hard palate

26. Facial bones Mandible makes up the lower jaw bone. Only movable skull bone other than auditory ossicles. The articulation of the condylar process with the mandibular fossa and articular tubercle of the temporal bone makes up the temperomandibular joint.

27. Facial bones Zygomatic bones�make up the cheekbones and part of lateral and floor of the orbits. Lacrimal bones�smallest bones of the face that make up medial wall of orbits. Houses the lacrimal sacs. Palatine bones�form posterior of hard palate and a small part of the orbital floors. Inferior nasal conchae�make up part of the nasal cavity. Vomer�a triangular bone that also makes up the floor of the nasal cavity.

28. Nasal cavity

29. Orbits The orbits house the eye and its structures. Seven bones make up the orbit

30. Sutures Immovable joints in adults between skull bones. The joints can be movable in infants and children. Coronal suture�unites frontal and parietal Sagittal suture�unites both parietal Lamboid suture�unites parietal and occipital Squamous suture�unites parietal and temporal

31. Fontanels Mesenchyme filled spaces that have not ossified.

32. Hyoid bone A unique bone that does not articulate with any other bone. It is suspended from the hyoid processes of the temporal bone. The hyoid bone and cartilages of the larynx are often fractured during strangulation.

33. Vertebral column Makes up to 2/5 of your height. Is composed of a series of bones called vertebrae and of connective tissues (fibrocartilage). It encloses and protects the spinal cord, which consists of nervous and connective tissues. It supports the head, serves as a point of attachment for the ribs, pelvic girdle and back muscles.

34. The Vertebrae There are 33 vertebrae during early development and 26 as an adult. 7 cervical vertebrae 12 thoracic vertebrae 5 lumbar vertebrae 1 sacrum (5 fused sacral vertebrae) 1 coccyx (4 fused coccygeal vertebrae)

35. Intervertebral discs Found in between the vertebrae from the second cervical to the sacrum. Consists of an outer ring of fibrocartilage called the annulus fibrosus and an inner soft, pulpy, highly elastic substance called nucleus pulposus.

36. Normal curves of the vertebral column Adult vertebral column has 4 curves Convex cervical Concave thoracic Convex lumbar Concave sacral Curves increase strength, balance, absorb shock and protects against fractures.

37. Normal curves of the vertebral column Fetus has a single anteriorly concave curve Primary curves-form during fetal development Concave thoracic Concave sacral Secondary curves-form in the 10 months after birth. Convex cervical Convex lumbar Curves are fully developed by age 10 but can be lost in old age.

38. Parts of a vertebra Body Thick anterior portion Has rough surface for attachment of intervertebral discs Anterior and lateral surfaces contain nutrient foramina

39. Parts of a vertebra Vertebral arch--joins with the body to make up the vertebral foramen. Pedicles Laminae The vertebral foramina make up the spinal cavity

40. Parts of a vertebra Vertebral notches�superior and inferior indentations in the pedicles Stacking of vertebral notches form openings called intervertebral foramen, which allow passage of spinal nerves to a particular body segment.

41. Parts of a vertebra Processes that form points of attachment for muscles Transverse Spinous

42. Parts of a vertebra Processes that form joints with superior and inferior vertebrae 2 Superior articular processes 2 Inferior articular processes Articulations are called intervertebral joints

43. Vertebral column regions: Cervical Have small bodies and large arches Have 3 large foramina: one vertebral and two transverse. The atlas (C1) is the first cervical vertebra inferior to the skull The axis (C2)

44. Vertebral column regions: Cervical Atlas (C1) Has no body but has anterior and posterior arches Superior articular surface is concave and articulates with occipital condyles Axis (C2) The dens projects superiorly through vertebral foramen of axis Vertebral prominens Atlas: Point out the pads on the atlas that let the head rest on the bones. The atlanto-occipital joints permits you to nod yes Axis � dens process � Body of the atlas is fused to the axis to form the dens (point out on the figure) Forms a pivot for rotation of the skull and atlas allowing side to side motions Children � have incomplete fusion between dens and atlas, so that impacts or severe shaking can cause severe damage to the spinal cord In adults, a blow to the base of the skull can dislocate the atlanto-axis joint and drive the dens into the base of the brain � this can be fatal. Vertebra prominens � last cervical vertebra. Interface between the cervical curve and thoracic curve Has prominent spinous process that you can feel in your neck � the first of the spinous processes Ligamentum nuchae � elastic ligament that stretches from the spinous process and attaches to the occipital bone of the skull � allows us to keep our head upright without expending any energy. Acts like bowstring. When you bend your head forward, it makes it easier to return your head to the upright position Atlas: Point out the pads on the atlas that let the head rest on the bones. The atlanto-occipital joints permits you to nod yes Axis � dens process � Body of the atlas is fused to the axis to form the dens (point out on the figure) Forms a pivot for rotation of the skull and atlas allowing side to side motions Children � have incomplete fusion between dens and atlas, so that impacts or severe shaking can cause severe damage to the spinal cord In adults, a blow to the base of the skull can dislocate the atlanto-axis joint and drive the dens into the base of the brain � this can be fatal. Vertebra prominens � last cervical vertebra. Interface between the cervical curve and thoracic curve Has prominent spinous process that you can feel in your neck � the first of the spinous processes Ligamentum nuchae � elastic ligament that stretches from the spinous process and attaches to the occipital bone of the skull � allows us to keep our head upright without expending any energy. Acts like bowstring. When you bend your head forward, it makes it easier to return your head to the upright position

45. Vertebral column regions: Cervical Atlas: Point out the pads on the atlas that let the head rest on the bones. The atlanto-occipital joints permits you to nod yes Axis � dens process � Body of the atlas is fused to the axis to form the dens (point out on the figure) Forms a pivot for rotation of the skull and atlas allowing side to side motions Children � have incomplete fusion between dens and atlas, so that impacts or severe shaking can cause severe damage to the spinal cord In adults, a blow to the base of the skull can dislocate the atlanto-axis joint and drive the dens into the base of the brain � this can be fatal. Vertebra prominens � last cervical vertebra. Interface between the cervical curve and thoracic curve Has prominent spinous process that you can feel in your neck � the first of the spinous processes Ligamentum nuchae � elastic ligament that stretches from the spinous process and attaches to the occipital bone of the skull � allows us to keep our head upright without expending any energy. Acts like bowstring. When you bend your head forward, it makes it easier to return your head to the upright position Atlas: Point out the pads on the atlas that let the head rest on the bones. The atlanto-occipital joints permits you to nod yes Axis � dens process � Body of the atlas is fused to the axis to form the dens (point out on the figure) Forms a pivot for rotation of the skull and atlas allowing side to side motions Children � have incomplete fusion between dens and atlas, so that impacts or severe shaking can cause severe damage to the spinal cord In adults, a blow to the base of the skull can dislocate the atlanto-axis joint and drive the dens into the base of the brain � this can be fatal. Vertebra prominens � last cervical vertebra. Interface between the cervical curve and thoracic curve Has prominent spinous process that you can feel in your neck � the first of the spinous processes Ligamentum nuchae � elastic ligament that stretches from the spinous process and attaches to the occipital bone of the skull � allows us to keep our head upright without expending any energy. Acts like bowstring. When you bend your head forward, it makes it easier to return your head to the upright position

46. Vertebral column regions: Cervical Atlas: Point out the pads on the atlas that let the head rest on the bones. The atlanto-occipital joints permits you to nod yes Axis � dens process � Body of the atlas is fused to the axis to form the dens (point out on the figure) Forms a pivot for rotation of the skull and atlas allowing side to side motions Children � have incomplete fusion between dens and atlas, so that impacts or severe shaking can cause severe damage to the spinal cord In adults, a blow to the base of the skull can dislocate the atlanto-axis joint and drive the dens into the base of the brain � this can be fatal. Vertebra prominens � last cervical vertebra. Interface between the cervical curve and thoracic curve Has prominent spinous process that you can feel in your neck � the first of the spinous processes Ligamentum nuchae � elastic ligament that stretches from the spinous process and attaches to the occipital bone of the skull � allows us to keep our head upright without expending any energy. Acts like bowstring. When you bend your head forward, it makes it easier to return your head to the upright position Atlas: Point out the pads on the atlas that let the head rest on the bones. The atlanto-occipital joints permits you to nod yes Axis � dens process � Body of the atlas is fused to the axis to form the dens (point out on the figure) Forms a pivot for rotation of the skull and atlas allowing side to side motions Children � have incomplete fusion between dens and atlas, so that impacts or severe shaking can cause severe damage to the spinal cord In adults, a blow to the base of the skull can dislocate the atlanto-axis joint and drive the dens into the base of the brain � this can be fatal. Vertebra prominens � last cervical vertebra. Interface between the cervical curve and thoracic curve Has prominent spinous process that you can feel in your neck � the first of the spinous processes Ligamentum nuchae � elastic ligament that stretches from the spinous process and attaches to the occipital bone of the skull � allows us to keep our head upright without expending any energy. Acts like bowstring. When you bend your head forward, it makes it easier to return your head to the upright position

47. Vertebral column regions: Thoracic Are larger and longer than cervical vertebrae. Spinous processes T1 and T2 T11 and T12 Spinous processes T1 and T2�long, laterally flattened and directed inferiorly T11 and T12- shorter, broader and directed posteriorlySpinous processes T1 and T2�long, laterally flattened and directed inferiorly T11 and T12- shorter, broader and directed posteriorly

48. Vertebral column regions: Thoracic Articulate with tubercles of the ribs Bodies have facets for articulating with heads of ribs. Articulation with ribs is called vertebrocostal joint Movement is limited by attachment of ribs to sternum Spinous processes T1 and T2�long, laterally flattened and directed inferiorly T11 and T12- shorter, broader and directed posteriorlySpinous processes T1 and T2�long, laterally flattened and directed inferiorly T11 and T12- shorter, broader and directed posteriorly

49. Vertebral column regions: Thoracic Spinous processes T1 and T2�long, laterally flattened and directed inferiorly T11 and T12- shorter, broader and directed posteriorlySpinous processes T1 and T2�long, laterally flattened and directed inferiorly T11 and T12- shorter, broader and directed posteriorly

50. Vertebral column regions: Lumbar Are the largest strongest vertebrae Have short thick processes Superior articular processes are medial instead of superior Inferior articular processes are lateral

51. Vertebral column regions: Lumbar Spinous processes project posterior

52. Vertebral column regions: Sacral Formed by the union of 5 sacral vertebrae Serves as foundation for the pelvic girdle Base�superior portion Apex--narrow inferior portion Fusion starts between 16 and 18 and is completed by age 30.Fusion starts between 16 and 18 and is completed by age 30.

53. Vertebral column regions: Sacral Fusion starts between 16 and 18 and is completed by age 30.Fusion starts between 16 and 18 and is completed by age 30.

54. Vertebral column regions: Sacral Fusion starts between 16 and 18 and is completed by age 30.Fusion starts between 16 and 18 and is completed by age 30.

55. Vertebral column regions: Coccyx Formed by the union of 4 coccygeal vertebrae Articulates with the apex of the sacrum In females coccyx points inferiorly In males coccyx points anteriorly Fusion starts later between age 20 and 30.Fusion starts later between age 20 and 30.

56. Bones of the thorax The thoracic cage is an enclosure made up of sternum, costal cartilages, ribs, and bodies of the thoracic vertebrae Protects thoracic organs and provides support for pectoral girdle and upper limbs

57. Thoracic bones: Sternum Flat narrow bone Manubrium is superior part Body is middle part Xiphoid process is the inferior smallest part-- does not ossify until age 40. Fuses by age 25. Manubrium articulates with costal cartilages of 1st and 2nd ribs. Also articulates with the medial ends of the claviclesManubrium articulates with costal cartilages of 1st and 2nd ribs. Also articulates with the medial ends of the clavicles

58. Thoracic bones: Ribs 12 pairs, increase in length from 1 to 7 Each rib articulates with corresponding thoracic vertebrae Ribs 1 to 7 (true ribs) articulate with sternum Ribs 8-12 are false ribs Ribs 11-12 are floating ribs.

59. Articulation of ribs with vertebrae Vertebrocostal joints�posterior portion connects to facet or demifacets of vertebra by its head and the rib tubercle connects to the transverse process.

60. Articulation of ribs with vertebrae

61. Rib injuries Breakage of ribs can happen at point of contact or weakest point (anterior to costal angle). Dislocated ribs indicate displacement of costal cartilage from sternum. Separated ribs are displace of a rib from its costal cartilage.

62. Temperomandibular joint syndrome (TMJ) Symptoms Dull pain around the ear, headache Tenderness of the jaw Clicking or popping sound when the jaw is opened. Limited opening of the mouth Abnormal wearing of teeth. Caused by improperly aligned teeth, grinding of teeth, arthritis or trauma to head or neck.